Hi MaxyMan,
I made mine for my defender. I used alloy box section, I purchased four lengths over two foot long each for a total of £4 at the Bristol and west rally, some longer bolts set me back another £2.
I just cut the box to length, took seat out at marked up the fixing holes like for like, drilled them out and bolted it all back in.
I will pop a picture up later if it will help, but both my front seats had a cost of £6, and does the same job.
Add to the fact you hardly ever look at them, a small bit of box has to be the way forward.